1 SD
  SD , short for SET DEFAULT, is a program to ease popping around the
  directory structure. It's advantage over the system SET DEFAULT
  command is that it allows you to specify a wildcarded file-spec.
  SD without any parameters will set your default to your login
  directory
  The symbol SD must be defined for you
      (i.e. $SD:==$DECUS:[EXE]SD)
  SD displays the directory moved to, preceded by ">" if it actually
  changed directories, and "=" if it didn't really move.
2 ^
  This is the same as "-", it moves you up one level.
  I.E. from USER$DISK_1:[DOE.JOHN] enter
        $SD ^
        > USER$DISK_1:[DOE]
  Note, you can have any number of these, one for each level you
  want to go up. (i.e. SD ^^^)
2 @
  This shows your current default directory
  I.E.
        $SD @
        = USER$DISK_1:[DOE.JOHN]
2 Examples
  So, for example, from your main directory you want to move down
  to some subdirectory that contains the file XXX.YYY, you could
  enter any of the following commands:
        SD [...]XXX.YYY
        SD ...]XXX.YYY
  note, for moving around you can leave off a whole heck of a lot,
  to move into subdirectory [.SUBDIR] you could enter any of the
  following:
        SD SUBDIR
        SD .SUBDIR
        SD [.SUBDIR
        SD .SUBDIR]
  and, of course, if it were your only subdirectory that started with
  "S" you could say:
        SD S*
        SD S*]
        SD .S*
		etcetera.
2 Restrictions
  Unlike a few of the CD commands, this command will not execute a LOGIN.COM
  file in the directory it moves to. If you need this capability, you must
  create a short command procedure like:
        $SD 'P1
        $@login

  Also, you cannot use a wildcarded directory-spec to SD into an empty
  directory (because SD basically looks for [dir-spec]*.*;* to determine
  where a directory is if it's wildcarded, and it can't find any files)
    So that, the following lines won't work:
        $CREATE/DIRECTORY [.NEWDIR]
        $SD [.new*]
    rather, you must specify the complete directory name if it is empty:
        $SD NEWDIR will work.
